function nodeList(name){
    this.name = name;
    this.next = null;
}

function splitList(head, target){
    let before  = new nodeList(0)
    let after = new nodeList(0)
    let aindex = after;
    let bindex = before;
    while(head){
        let node = new nodeList(head.val)
        if(head.val >= target){
            aindex.next = node;
            aindex = aindex.next;
        }else {
            bindex.next = node;
            bindex = bindex.next;
        }

        head = head.next
    }

    bindex.next = aindex.next // 去掉aindex的头
    return bindex.next // 去掉b的头
}